Method and apparatus for battery charging with constant current, constant voltage, and pulsed charging

ABSTRACT

A battery charging apparatus includes a voltage detecting circuit, a current detecting circuit, a charging circuit, and a charge control circuit. The voltage detecting circuit detects a battery voltage of the battery and accordingly outputs a signal. The current detecting circuit detects a battery current supplied to the battery and accordingly outputs a signal. The charging circuit executes a current supply control to perform the charging to the battery such that the battery voltage becomes equal to a voltage predetermined based on control signals and also that the charging current becomes equal to a current predetermined based on the control signals. The charge control circuit instructs the charging circuit with the control signals to set the battery voltage and the charge current in response to a voltage indicated by the signal from the voltage detecting circuit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation application of U.S. patentapplication Ser. No. 10/626,732, filed on Jul. 25, 2003, which claimspriority from Japanese patent application; No. JPAP2002-221390, filed onJul. 30, 2002 in the Japanese Patent Office, the entire disclosure ofboth of which are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for batterycharging, and more particularly to a method and apparatus for batterycharging to a nonaqueous second battery efficiently using constantcurrent charging, constant voltage charging, and pulse charging incombination.

BACKGROUND OF THE INVENTION

Conventionally, continuous charging and pulse charging are commonmethods for charging a nonaqueous second battery such as a lithium ionbattery, an Ni-MH battery, etc. Continuous charging may be grouped intoCC (constant current) charging, CV (constant voltage) charging, and CCCV(constant-current constant-voltage) charging, which combines the CCcharging and the CV charging. In the charging of a nonaqueous secondbattery, it is necessary to exercise due care to avoid an excesscharging voltage exceeding a predetermined voltage since such anexcessive charging voltage considerably deteriorates the batteryperformance.

Thus, in order to avoid excessive charging voltage, the CCCV charging isgenerally used as the continuous charging method. In the CCCV chargingmethod, charging with a constant current is performed at an early stageof the charging to the second battery and charging with a constantvoltage is subsequently performed after a battery voltage of the secondbattery reaches a predetermined voltage. When the charging current (alsoreferred to herein as “charge current” and “battery current”) is reducedto a predetermined value, the second battery is in a fully-charged stateand the charging is completed. One advantage of this method is thepossibility of rapid charging by setting the charging current used inthe constant current charging during the early stage of the charging toa relatively large value. Another advantage is the prevention ofdeterioration of the second battery due to application of excessivevoltage since the charging mode is shifted from CC charging to CVcharging when the battery voltage of the second battery reaches apredetermined voltage.

However, when the constant current used in the initial charging stage isset to an excessively large value, a heat production by the secondbattery becomes large, which causes several problems: a reduction ofcharging efficiency, an acceleration of deterioration with respect tothe second battery, etc. On the other hand, pulse charging has anadvantage of less deterioration to the second battery because pulsecharging is provided with pause times at certain intervals during thecharging period, which increases efficiency of electrochemical changes.Additionally, pulse charging allows a relatively large charging currentand therefore, is suitable for rapid charging as well.

For example, Japanese Laid-Open Patent Application Publication No.2001-169471 describes a second battery charging apparatus that featuresadvantages of both continuous charging and pulse charging. Thisapparatus attempts to avoid over-charging while suppressing heatproduction of the second battery. That is, the continuous charging isperformed during the initial charging and the charging mode is switchedto the pulse charging when the battery voltage in the charging exceeds apredetermined voltage V1 depending on battery temperature. When thebattery voltage with an open circuit in pulse charging exceeds apredetermined voltage V3, the mode is switched from the pulse chargingto the continuous charging. Then, the charging is stopped when thebattery voltage in the second battery reaches a predetermined voltageV2.

For such a charging apparatus, miniaturization has increasingly been anissue recently, as mobile equipment such as cellular phones and the likeusing a second battery becomes widespread. In particular, chargingapparatus for cellular phones are often carried along with a cellularphone. Such mobility requires a relatively short charging time to makethe cellular phone operable and also requires a compact and light bodyproducing less heat. The charge required to make the cellular phoneoperable may not be a full charge. The charge time to reach less thanfully-charged state may be correspondingly less than the time to fullycharge the second battery.

However, conventional charging apparatus have been designed with a viewmainly to reducing a charging time to the full-charge state and/orsuppressing a temperature rise of the battery. To reduce the chargingtime, it is necessary to charge with a relatively large current. As aresult, the charging apparatus produces a relatively large amount ofheat and accordingly the size of the charging apparatus may becomelarge. Since the temperature of the second battery rises, a temperaturedetection mechanism is additionally needed, resulting in an increase ofthe size and complexity of the apparatus itself. In addition, chargingwith such large current often accelerates deterioration of ionizationwith respect to the second battery.

BRIEF SUMMARY OF THE INVENTION

The present invention provides battery charging techniques capable ofperforming a quick charge to a second battery while suppressing heatproduction and deterioration of the second battery.

In one example, a novel second battery charging apparatus includes avoltage detecting circuit, a current detecting circuit, a chargingcircuit, and a charge control circuit. The voltage detecting circuitdetects a battery voltage of the second battery and outputs a signal inresponse to the battery voltage detected. The current detecting circuitdetects a battery current supplied to the second battery and outputs asignal in response to the battery current detected. The charging circuitcontrols a current supply to the second battery to perform the chargingof the second battery until the battery voltage detected by the voltagedetecting circuit becomes substantially equal to a battery voltagepredetermined in response to a first input control signal appliedthereto also such that the charging current detected by the currentdetecting circuit becomes substantially equal to a charging currentpredetermined in response to a second input control signal appliedthereto. The charge control circuit instructs the charging circuit bysending the input control signals to set the battery voltage and thecharge current in response to a voltage indicated by the signal outputfrom the voltage detecting circuit.

The charge control circuit may instruct the charging circuit to performa constant current charging in which a charging is performed flowing afirst constant current to the second battery and subsequently anothercharging is performed flowing a second constant current greater than thefirst current to the second battery when the battery voltage of thesecond battery is smaller than a second pre-set voltage. Further, thecharge control circuit may instruct the charging circuit to alternatelyflow a second constant current to the second battery and pause the flowof the second constant current to the second battery, for a pre-settime. Pausing the second constant current flow stops the chargingcurrent to the second battery.

The charge control circuit may instruct the charging circuit to controlthe charging current flowing to the second battery such that the batteryvoltage becomes substantially equal to a third constant voltage duringthe constant current charging during the pulse charging cycle and alsosuch that the battery voltage becomes substantially equal to the firstconstant voltage smaller than a third constant voltage during the pauseduring the pulse charging cycle.

The charge control circuit may instruct the charging circuit to performthe constant current charging to supply the second constant current tothe second battery when the battery voltage becomes substantially equalto a third pre-set voltage greater than the second pre-set voltage andalso to perform the constant voltage charging to control the chargingcurrent such that the battery voltage becomes substantially equal to thethird constant voltage when the battery voltage becomes substantiallyequal to a fourth pre-set voltage greater than the third pre-setvoltage.

The charge control circuit may instruct the charging circuit to controlthe charging current flowing through the second battery such that thebattery voltage becomes substantially equal to the third constantvoltage during the constant current charging before pulse charging isperformed.

The charge control circuit may instruct the charging circuit to controlthe charging current flowing through the second battery such that thebattery voltage becomes substantially equal to the first constantvoltage when the battery voltage is smaller than the first pre-setvoltage which is smaller than the second pre-set voltage. The chargecontrol circuit may further instruct the charging circuit to control thecharging current flowing through the second battery such that thebattery voltage becomes substantially equal to the second constantvoltage, which is smaller than the third constant voltage and greaterthan the first constant voltage, during constant current charging beforepulse charging is performed.

The charging circuit may include a constant voltage generating circuit,a signal switching circuit, a voltage switching circuit, a controltransistor, and a control circuit. The constant voltage generatingcircuit generates first, second, and third constant voltages. Thevoltage switching circuit selects and outputs one of the first and thirdconstant voltages output from the constant voltage generating circuit inresponse to the control signals from the charge control circuit. Thecontrol transistor outputs a current to the second battery in responseto an input control signal applied thereto. The control circuit controlsthe control transistor such that the battery voltage represented by asignal output from the voltage detecting circuit becomes substantiallyequal to a voltage represented by a signal output from the voltageswitching circuit and such that the charging current represented by asignal output from the current detecting circuit becomes substantiallyequal to a constant current represented by a signal output from thesignal switching circuit.

The above-mentioned charging apparatus may further include a charge-enddetecting circuit that determines an event that charging is completedrelative to the second battery and outputs a predetermined signal whenthe charging current detected by the current detecting circuit becomeslower than the first constant current. In this case, the charge controlcircuit causes the charging circuit to stop charging upon receiving thesignal indicative of a charge-end output from the charge-end detectingcircuit.

The first constant voltage may be a voltage greater than an overdischarge voltage of the second battery and the third constant voltagemay be a voltage substantially equal to a full charge voltage of thesecond battery.

The current detecting circuit may include a resistor and a currentdetector. The resistor passes the charging current to be supplied to thesecond battery. The current detector detects the charging current basedon a voltage across the resistor and outputs a signal in response to thedetected charging current. In this case, the voltage detecting circuit,the current detector of the current detecting circuit, the chargecontrol circuit, the charge-end detecting circuit, and severalcomponents of the charging circuit including the constant voltagegenerating circuit, the voltage switching circuit, the constant currentreference signal generating circuit, the signal switching circuit, andthe voltage switching circuit are integrated into a single integratedcircuit chip.

The current detecting circuit may include a resistor and a currentdetector. The resistor passes the charging current to be supplied to thesecond battery. The current detector detects the charging current basedon a voltage across the resistor and outputs a signal in response to thedetected charging current. In this case, the voltage detecting circuit,the current detector of the current detecting circuit, the chargecontrol circuit, the charge-end detecting circuit, the and severalcomponents of the charging circuit including the constant voltagegenerating circuit, the voltage switching circuit, the constant currentreference signal generating circuit, the signal switching circuit, andthe voltage switching circuit are integrated into a single integratedcircuit chip.

The second battery may be a nonaqueous second battery such as a lithiumion battery.

In one example, a charging method for a second battery includes the actsof: performing a first constant current charging by supplying a firstconstant current to the second battery when a battery voltage of thesecond battery is smaller than a first set voltage; performing a secondconstant current charging by supplying a second constant current greaterthan the first constant current to the second battery when the batteryvoltage of the second battery is greater than the first pre-set voltage;pulse charging of the second battery when the battery voltage of thesecond battery becomes equal to or greater than a second pre-setvoltage, which is greater than the first pre-set voltage by alternatelycarrying out at intervals of a predetermined time period constantcurrent charging, in which the second constant current is supplied tothe second battery and a pausing in which the supply of the chargingcurrent is stopped.

The pulse charging act may include controlling the charge current to thesecond battery such that the battery voltage of the second batterybecomes substantially equal to a third constant voltage and such thatthe battery voltage of the second battery becomes substantially equal toa first constant voltage smaller than a third constant voltage duringthe pause in the pulse charging act.

The above-mentioned charging method may further include acts of constantcurrent charging, in which the constant current charging with the secondconstant current is performed to the second battery when the batteryvoltage of the second battery becomes substantially equal to the thirdpre-set voltage, which is equal to or greater than the second pre-setvoltage and constant voltage charging, in which the charging current iscontrolled such that the battery voltage of the second battery becomessubstantially equal to the third constant voltage when the batteryvoltage of the second battery becomes substantially equal to a fourthpre-set voltage equal to or greater than the third pre-set voltage.

The charging current to the second battery may be controlled such thatthe battery voltage of the second battery becomes substantially equal tothe third constant voltage during the first and second constant currentcharging.

The charging current to the second battery may be controlled such thatthe battery voltage of the second battery becomes substantially equal tothe first constant voltage when the battery voltage of the secondbattery is smaller than the first pre-set voltage during the firstconstant current charging and such that the battery voltage of thesecond battery becomes substantially equal to the second constantvoltage, which is less than the third constant voltage and greater thanthe first constant voltage during the first constant current charging.

The above-mentioned charging method may further include acts ofdetermining that the charging is completed when the charging current tothe second battery becomes substantially equal to a predeterminedcurrent value smaller than the first constant current and subsequentlyterminating the charging to the second battery.

The second battery may be a nonaqueous second battery such as a lithiumion battery.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a nonaqueous second battery charging apparatus according apreferred embodiment of the present invention;

FIG. 2 is a time chart for explaining a charging operation performed bythe charging apparatus of FIG. 1;

FIGS. 3, 3A, and 3B show a flowchart of an exemplary procedure of thecharging operation performed by the charging apparatus of FIG. 1;

FIG. 4 is a nonaqueous second battery charging apparatus accordinganother preferred embodiment of the present invention;

FIG. 5 is a time chart for explaining a charging operation performed bythe charging apparatus of FIG. 4; and

FIGS. 6, 6A, and 6B show a flowchart of an exemplary procedure of thecharging operation performed by the charging apparatus of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

In describing preferred embodiments illustrated in the drawings,specific terminology is employed for the sake of clarity. However, thedisclosure of this patent specification is not intended to be limited tothe specific terminology so selected and it is to be understood thateach specific element includes all technical equivalents that operate ina similar manner. Referring now to the drawings, wherein like referencenumerals designate identical or corresponding parts throughout theseveral views, particularly to FIG. 1, a description is made for anonaqueous-second-battery charging apparatus 1 according to a preferredembodiment of the present invention. The charging apparatus 1 of FIG. 1includes a lithium ion battery as a nonaqueous second battery and isused in a cellular phone, for example.

As shown in FIG. 1, the charging apparatus 1 includes an adapterdetecting circuit 2, a voltage detecting circuit 3, a CCCV(constant-current constant-voltage) charging circuit 4, a resistor 5, acurrent detecting circuit 6, a charge-end detecting circuit 7, and acharge control circuit 8. The adapter detecting circuit 2 detects apower source voltage Vd applied thereto by an AC (alternating current)adapter 10 and generates a specific current when the power sourcevoltage Vd exceeds a predetermined voltage. The voltage detectingcircuit 3 detects a positive voltage Vb of a lithium ion battery 11which is a nonaqueous second battery and outputs a signal in response tothe positive voltage Vb detected. The positive voltage of the lithiumion battery 11 is hereinafter referred to as a battery voltage. The CCCVcharging circuit 4 charges the lithium ion battery 11 with aconstant-current constant-voltage charge. The resistor 5 converts acharging current ib flowing from the CCCV charging circuit 4 to thelithium ion battery 11 into a voltage. The current detecting circuit 6detects the charging current ib based on a detection of a voltage acrossthe resistor 5 and outputs a signal in response to the charging currentib detected. The charge-end detecting circuit 7 detects an event thatthe charge to the lithium ion battery 11 has been completed based on thesignal output from the current detecting circuit 6 and, upon detectingsuch event, outputs a predetermined signal. The charge control circuit 8controls operations of the CCCV charging circuit 4 in response to thesignals output from the adapter detecting circuit 2, the voltagedetecting circuit 3, and the charge-end detecting circuit 7.

The CCCV charging circuit 4 includes a CCR (constant current reference)signal generating circuit 21, a constant voltage generating circuit 22,a signal switching circuit 23, a voltage switching circuit 24, a controltransistor 25, a control circuit 26, and a diode 27. The CCR signalgenerating circuit 21 generates and outputs a first constant currentreference (CCR) signal S1 indicative of a first predetermined constantcurrent i1 and a second constant current reference signal S2 indicativeof a second predetermined constant current i2, in which the secondpredetermined constant current i2 is greater than the firstpredetermined constant current i1. It should be noted that the firstpredetermined constant current i1 is in the range of several to a fewtens of milliampere in the lithium ion battery 11. The constant voltagegenerating circuit 22 generates and outputs a first predeterminedconstant voltage V1, a second predetermined constant voltage V2, a thirdpredetermined constant voltage V3, and a fourth predetermined constantvoltage V4.

The signal switching circuit 23 selects one of the first CCR signal S1and the second CCR signal S2 from the CCR signal generating circuit 21in response to a control signal from the charge control circuit 8 andoutputs the selected signal to the control circuit 26. The voltageswitching circuit 24 selects one of the first predetermined constantvoltage V1 and the third predetermined constant voltage V3 from theconstant voltage generating circuit 22 in response to a control signalfrom the charge control circuit 8 and outputs the selected signal to thecontrol circuit 26. The control transistor 25 includes a P-channel MOS(metal oxide semiconductor) transistor and controls a supply of thecurrent from the AC adaptor 10 to the lithium ion battery 11. Thecontrol circuit 26 controls operations of the control transistor 25 inresponse to the signals from the voltage detecting circuit 3, thecurrent detecting circuit 6, the signal switching circuit 23, and thevoltage switching circuit 24.

The resistor 5, the control transistor 25, the diode 27, and the lithiumion battery 11 are connected in series between a power supply terminalto which the power from the AC adapter 10 is supplied and the ground sothat the charging current is supplied to the lithium ion battery 11. Thediode 27 prevents a reverse current flow from the lithium ion battery 11to the AC adapter 10 when the voltage at the power source terminal 15 issmaller than the battery voltage Vb of the lithium ion battery 11.

Several components shown in FIG. 1 can be integrated into a single IC(integrated circuit) chip, including the adapter circuit 2, the voltagedetecting circuit 3, the current detecting circuit 6, the charge-enddetecting circuit 7, the charge control circuit 8, and severalcomponents of the CCCV charging circuit 4 including the constant currentreference signal generating circuit 21, the constant voltage generatingcircuit 22, the signal switching circuit 23, the voltage switchingcircuit 24, and the control circuit 26. In addition, the diode 27 canalso be integrated into the above-mentioned single IC chip.

When the AC adapter 10 is connected to the power source terminal 15, thevoltage at the power source terminal 15 rises over a predeterminedvoltage. Upon detecting the rise of the voltage at the power sourceterminal 15 to the predetermined voltage, the adapter detecting circuit2 outputs a signal to the charge control circuit 8 indicating that thepower is supplied. The voltage detecting circuit 3 outputs signals tothe charge control circuit 8 and the control circuit 26 in response tothe battery voltage Vb being detected. The control circuit 26 controls agate voltage of the control transistor 25 in response to the signalssent from the voltage detecting circuit 3, the current detecting circuit6, the signal switching circuit 23, and the voltage switching circuit 24so as to control the charging current ib and the battery voltage Vb withrespect to the lithium ion battery 11. The current detecting circuit 6outputs signals to the charge-end detecting circuit 7 and the controlcircuit 26 in response to the charging current ib detected across theresistor 5. The charge-end detecting circuit 7 outputs a predeterminedcharge-end signal Sce to the charge control circuit 8 upon detecting,based on the signal from the current detecting circuit 6, an event thatthe charging current ib is reduced to a predetermined charge-end currenti3 indicative of a charge completion.

The charge control circuit 8, receiving the constant voltages V1-V4output from the constant voltage generating circuit 22, controls theoperations of the signal switching circuit 23 and the voltage switchingcircuit 24 in response to the signals sent from the adapter detectingcircuit 2, the voltage detecting circuit 3, and the charge-end detectingcircuit 7. The signal switching circuit 23, receiving the firstpredetermined CCR signal S1 and the second predetermined CCR signal S2output from the CCR signal generating circuit 21, selects one of thefirst and second predetermined CCR signals S1 and S2 in response to thecontrol signal from the charge control circuit 8 and outputs theselected signal to the control circuit 26. The voltage switching circuit24, receiving the first and third constant voltage V1 and V3 from theconstant voltage generating circuit 22, exclusively selects one of thefirst and third constant voltages V1 and V3 in response to the controlsignal output from the charge control circuit 8 and outputs the selectedvoltage to the control circuit 26.

The control circuit 26 controls the control transistor 25 such that thevoltage input from the voltage detecting circuit 3 becomes substantiallyequal to the constant voltage input from the voltage switching circuit24 and that the charging current ib represented by the signal input fromthe current detecting circuit 6 becomes substantially equal to theconstant current represented by the signal input from the signalswitching circuit 23.

Referring to FIG. 2, an exemplary operation of the charging apparatus 1is explained. In FIG. 2, three time charts are combined together using acommon time span, in which A1, A2, and A3 represent characteristiccurves of the battery voltage Vb, the charging current ib, and a voltageVa output from the voltage switching circuit 24. In FIG. 2, Ts and Terepresent time points of a charge start and a charge end, respectively.Likewise, T1, T2, T3, T4, and T5 represent time periods of a pre-charge,a quick charge, a pulse charge, a constant current charge, and aconstant voltage charge, respectively.

In FIG. 2, the charge control circuit 8, receiving the first, second,third, and fourth predetermined constant voltages V1-V4, generates afirst pre-set voltage Vs1 based on the first predetermined constantvoltage V1, a second pre-set voltage Vs2 based on the secondpredetermined constant voltage V2, a third pre-set voltage Vs3 based onthe third predetermined constant voltage V3, and a fourth pre-setvoltage Vs4 based on the fourth predetermined constant voltage V4. Withthis configuration, it becomes possible to eliminate an extra powersource to generate power to be used by the CCCV charging circuit 4. Inthe above configuration, the voltages are determined to meetrelationships of V4>V3>V2>V1 and Vs4>Vs3>Vs2>Vs1.

For example, the above-mentioned voltages V1-V4 are set as follows. Thefourth predetermined constant voltage V4 is pre-set to a voltageexceeding an over-discharge voltage of the lithium ion battery 11. Thethird predetermined constant voltage V3 is pre-set to a voltage, whichthe lithium ion battery 11 will have at a fully-charged state. Thesecond predetermined constant voltage V2 is pre-set to a voltage atwhich a load can be activated. The first pre-set voltage Vs1 is set in arange of from 2.0 volts to 2.2 volts, in cases where a lithium ionbattery is used.

After the AC adapter 10 is connected to the power source terminal 15,the charge control circuit 8 receives a signal from the adapterdetecting circuit 2 indicating an event that the power is applied. Then,the charge control circuit 8 starts the charge control at time point Ts.The charge control circuit 8 controls the signal switching circuit 23 tooutput the first predetermined CCR signal S1 and the voltage switchingcircuit 24 to output the third predetermined constant voltage V3. Basedon these actions, the control circuit 26 controls the operations of thecontrol transistor 25 such that the battery voltage Vb indicated by thesignal from the voltage detecting circuit 3 is substantially equal tothe third predetermined constant voltage V3 and such that the signalfrom the current detecting circuit 6 indicates that the current ib issubstantially equal to the first predetermined constant current i1, sothat the lithium ion battery 11 is pre-charged during the time periodT1.

The above-mentioned pre-charge cycle is a preliminary charging processfor charging the lithium ion battery 11 with a relatively small currentuntil the battery voltage Vb reaches the first pre-set voltage Vs1. Thisis because a quick charge with a relatively large current to the lithiumion battery 11 in an over-discharged state will cause various problems,for example, a deterioration of the lithium ion battery 11 may beaccelerated. A relatively large current may also cause the controltransistor 25 functioning as a control element may suffer a relativelylarge loss of electric power which causes a production of a relativelylarge amount of heat at the charging apparatus 1.

When the battery voltage Vb becomes substantially equivalent to thefirst set voltage Vs1, the charge control circuit 8 controls the signalswitching circuit 23 to output the second predetermined CCR signal S2and the third predetermined constant voltage V3 to continue being outputto the voltage switching circuit 24. Based on these actions, the controlcircuit 26 controls the operations of the control transistor 25 suchthat the battery voltage Vb indicated by the signal from the voltagedetecting circuit 3 is substantially equal to the third predeterminedconstant voltage V3 and such that the signal from the current detectingcircuit 6 indicates that the current ib is substantially equal to thesecond predetermined constant current i2, so that a quick charge isperformed relative to the lithium ion battery 11 during the time periodT2. The quick charge is applied to quickly charge the lithium ionbattery 11 to a state at which the lithium ion battery 11 can activatethe load.

When the battery voltage Vb reaches the second pre-set voltage Vs2, thecharge control circuit 8 controls the signal switching circuit 23 tocontinue to output the second predetermined CCR signal S2 and thevoltage switching circuit 24 to output the first predetermined constantvoltage V1. Accordingly, the control circuit 26 controls the operationsof the control transistor 25 such that the battery voltage Vb indicatedby the signal from the voltage detecting circuit 3 is substantiallyequal to the first predetermined constant voltage V1 and that the signalfrom the current detecting circuit 6 is substantially equal to thesecond predetermined constant current i2. In this case, since thebattery voltage Vb is already greater than the first predeterminedconstant voltage V1, the control circuit 26 controls the controltransistor 25 to turn off the pulse charging (an interruption state) sothat the battery current ib to the lithium ion battery 11 does not flow.

When a predetermined time ta is elapsed, the charge control circuit 8controls the signal switching circuit 23 to continue to output thesecond predetermined CCR signal S2 and the voltage switching circuit 24to output the third predetermined constant voltage V3. Accordingly, thecontrol circuit 26 controls the operations of the control transistor 25such that the battery voltage Vb indicated by the signal from thevoltage detecting circuit 3 is substantially equal to the thirdpredetermined constant voltage V3 and that the signal from the currentdetecting circuit 6 indicates that the current ib is substantially equalto the second predetermined constant current i2. In this case, since thebattery voltage Vb is smaller than the third predetermined constantvoltage V3, the control circuit 26 controls the control transistor 25such that the charging current ib flows to the lithium ion battery 11until the current ib becomes substantially equal to the second constantcurrent i2.

When a predetermined time tb is elapsed, the charge control circuit 8controls the signal switching circuit 23 to continue to output thesecond predetermined CCR signal S2 and the voltage switching circuit 24to output again the first predetermined constant voltage V1. The chargecontrol circuit 8 repeats the above-described operations until thebattery voltage Vb becomes substantially equal to the third pre-setvoltage Vs3. This repetitive charge process is pulse charging performedduring the time period T3. During the time period T3 for the pulsecharging, most of the capacity of the lithium ion battery 11 is charged.The pulse charge performed during the time period T3 produces an averagecharging current flowing through the control transistor 25 and which isapproximately one half of the quick charge current value. Therefore,while the pulse charge generally takes a longer charging time than thecontinuous charge, the control transistor 25 is driven with less heatproduction. This contributes to the miniaturization of the chargingapparatus 1 and, at the same time, to the reduction of the heatproduction in the lithium ion battery 11 so that the lithium ion battery11 will have a relatively long life.

When the battery voltage Vb reaches the third pre-set voltage Vs3, thecharge control circuit 8 controls the signal switching circuit 23 tocontinue to output the second predetermined CCR signal S2 and thevoltage switching circuit 24 to output the third predetermined constantvoltage V3. Accordingly, the control circuit 26 controls the operationsof the control transistor 25 such that the battery voltage Vb indicatedby the signal from the voltage detecting circuit 3 is substantiallyequal to the third predetermined constant voltage V3 and that the signalfrom the current detecting circuit 6 indicates that the charging currentib is substantially equal to the second predetermined constant currenti2. Thus, the constant current charge is performed during the timeperiod T4. The constant current charge is performed following thecompletion of pulse charging and is completed upon an accurate detectionof the full-charge. This constant current charge is the first half ofthe CCCV charging process.

When the charge process is shifted from pulse charging to continuouscharging (i.e., the continuous current charge in the CCCV charge), theaverage charge current is increased but is still smaller than that ofthe quick charge since the battery voltage Vb is sufficiently increasedduring the time period T3 by pulse charging. This suppresses the heatproduction by the control transistor 25 for a relatively short timeperiod. The electric power consumed by the control transistor 25 can beexpressed by a value obtained by multiplying the charge current ib by adifference between the power source voltage Vd and the battery voltageVb. Accordingly, the electric power consumed by the control transistor25 becomes small as the battery voltage Vb increases.

The charge current ib is then gradually reduced when the battery voltageVb is increased to a value substantially equal to the fourth pre-setvoltage Vs4. Since the fourth pre-set voltage Vs4 is set to thefull-charge voltage value of the lithium ion battery 11, the controlcircuit 26 naturally shifts its charge mode from the CC (constantcurrent) charge to the CV (constant voltage) charge. When the charge-enddetecting circuit 7 detects from the signal output by the currentdetecting circuit 6 an event that the charge current ib is decreased toa value smaller than the predetermined current value i3, the charge-enddetecting circuit 7 sends the predetermined charge-end signal Sce to thecharge control circuit 8, which occurs at the time point Te. Theconstant voltage charge is performed during the time period T5, whichstarts from the end of the time period T4 and continues to the timepoint Te. Upon receiving the predetermined charge-end signal Sce, thecharge control circuit 8 determines that the charge to the lithium ionbattery 11 is completed. In this way, the charging apparatus 1 canaccurately detect the fully-charged state of the lithium ion battery 11by performing the constant current charge and subsequently the constantvoltage charge during the last stage of the charging process.

Referring to FIGS. 3, 3A, and 3B, an exemplary procedure of theoperation performed by the charge control circuit 8 is explained. StepsS1 to S7 are shown in FIG. 3A and Steps S8 to S13 are shown in FIG. 3B.In Step S1 of FIG. 3A, the charge control circuit 8 determines whetherit receives the signal from the adapter circuit 2 indicating that thepower is supplied. The process of Step S1 is continued until the signal,that power is supplied, is received. When the signal is determined asbeing received, the charge control circuit 8 performs the pre-chargeprocess, in Step S2. That is, the charge control circuit 8 controls thesignal switching circuit 23 to output the first predetermined CCR signalS1 and the voltage switching circuit 24 to output the thirdpredetermined constant voltage V3.

Then, in Step S3, the charge control circuit 8 determines whether thebattery voltage Vb is substantially equal to or greater than the firstpre-set voltage Vs1. The process of Step S3 continues until the batteryvoltage Vb is determined to be substantially equal to or greater thanthe first pre-set voltage Vs1. When the battery voltage Vb is determinedto be substantially equal to or greater than the first set voltage Vs1,the charge control circuit 8 performs the quick charge, in Step S4. Thatis, the charge control circuit 8 controls the signal switching circuit23 to output the second predetermined CCR signal S2 and the voltageswitching circuit 24 to continue to output the third predeterminedconstant voltage V3.

Then, in Step S5, the charge control circuit 8 determines whether thebattery voltage Vb is substantially equal to or greater than the secondpre-set voltage Vs2. The process of Step S5 continues until the batteryvoltage Vb is determined to be substantially equal to or greater thanthe second pre-set voltage Vs2. When the battery voltage Vb isdetermined to be substantially equal to or greater than the second setvoltage Vs2, the process proceeds to Step S6 in which the charge controlcircuit 8 performs a charge hibernation. During charge hibernation, thecharge process to the lithium ion battery 11 is paused. That is, thecharge control circuit 8 controls the signal switching circuit 23 tocontinue to output the second predetermined CCR signal S2 and thevoltage switching circuit 24 to output the first predetermined constantvoltage V1. Then, in the predetermined time period ta after the chargehibernation commences, the charge control circuit 8 restarts, in StepS7, the charge process to the lithium ion battery 11 by controlling theCCR signal generating circuit 21 to continue to output the secondpredetermined CCR signal S2 to the signal switching circuit 23 and theconstant voltage generating circuit 22 to output the third predeterminedconstant voltage V3 to the voltage switching circuit 24.

Then, in Step S8, the charge control circuit 8 determines whether thebattery voltage Vb is substantially equal to or greater than the thirdset voltage Vs3. The process of Step S8 continues until the batteryvoltage Vb is determined to be substantially equal to or greater thanthe third pre-set voltage Vs3. When the battery voltage Vb is determinedto be substantially equal to or greater than the third pre-set voltageVs3, the charge control circuit 8 performs the constant current charge,in Step S9. That is, the charge control circuit 8 controls the signalswitching circuit 23 to continue to output the second predetermined CCRsignal S2 and the voltage switching circuit 24 to output the thirdpredetermined constant voltage V3.

Then, in Step S10, the charge control circuit 8 determines whether thebattery voltage Vb is substantially equal to or greater than the fourthset voltage Vs4. The process of Step S10 continues until the batteryvoltage Vb is determined to be substantially equal to the pre-setvoltage Vs4. When the battery voltage Vb is determined to besubstantially equal to or greater than the fourth set voltage Vs4, thecharge control circuit 8 allows the shift of the charge process, in StepS11. That is, in this situation, the battery current ib is graduallyreduced and accordingly the charge is naturally shifted from theconstant current charge to the constant voltage charge. Then, in StepS12, the charge control circuit 8 determines whether an event occursthat the battery current ib becomes smaller than the predeterminedcurrent value i3 and accordingly the charge control circuit 8 receivesthe predetermined charge-end signal Sce from the charge-end detectingcircuit 7. The charge control circuit 8 continues the process of StepS12 until the charge-end signal Sce is received. When such event isdetermined as having occurred, the charge control circuit 8 determinesthat the charge process relative to the lithium ion battery 11 iscompleted and terminates the charge process, in Step S13.

In this way, the charging apparatus 1 detects an event that the batteryvoltage Vb exceeds the second pre-set voltage Vs2. Then, the chargingapparatus 1 performs the pulse charge by outputting the secondpredetermined CCR signal S2 to the signal switching circuit 23 as wellas the first predetermined constant voltage V1 during the predeterminedtime period ta and subsequently the third predetermined constant voltageV3 during the predetermined time period tb to the voltage switchingcircuit 24 until the time the battery voltage Vb becomes the third setvoltage Vs3, as described above. In this charging apparatus 1, thesecond pre-set voltage Vs2 is set to a value, with which the load thelithium ion battery 11 supplies power to can operate.

Accordingly, the charging time to make the lithium ion battery 11sufficiently charged to drive the load can be almost the same as thatfor the conventional rapid charging method. After that, the chargingapparatus 1 changes the charge mode to the pulse charge mode in whichthe battery voltage Vb and the charge current ib are regulated to therespective values, as described above, so as to decrease the averagecharge current. Thereby, the heat production by the nonaqueous secondbattery and the control element can be suppressed so thatminiaturization of the charging apparatus can be achieved. Moreover,this configuration can reduce the deterioration of the nonaqueous secondbattery. In addition, an accurate detection of an event that thenonaqueous second battery is fully-charged can be achieved by thearrangement in which the CCCV charging process is performed after thepulse charge.

Next, a nonaqueous-second-battery charging apparatus 100 according toanother preferred embodiment of the present invention is explained withreference to FIG. 4. The charging apparatus 100 of FIG. 4 is similar tothe charging apparatus 1 of FIG. 1, except for a CCCV (constant-currentconstant-voltage) charging circuit 104 and a charge control circuit 108.The CCCV charging circuit 104 is similar to the CCCV charging circuit 4of FIG. 1, except for the constant voltage generating circuit 122 andthe voltage switching circuit 124 to handle the first, second, and thirdconstant voltages V1-V3 to perform a three-step change of the voltage Vaoutput from the voltage switching circuit 124. The charge controlcircuit 108 is similar to the charge control circuit 8 of FIG. 1, exceptfor a circuit portion (not shown) handling the above-mentionedthree-step change of the voltage Va.

The charge control circuit 108 receives the first through to fourthconstant voltages V1-V4 from the constant voltage generating circuit122, controls the operations of the signal switching circuit 23 and thevoltage switching circuit 124 in response to the signals sent from theadapter detecting circuit 2, the voltage detecting circuit 3, and thecharge-end detecting circuit 7. The signal switching circuit 23 receivesthe first predetermined CCR signal S1 and the second predetermined CCRsignal S2 output from the CCR signal generating circuit 21, and selectsone of the first and second predetermined CCR signals S1 and S2 inresponse to the control signal from the charge control circuit 108. Theselected signal is output to the control circuit 26. The voltageswitching circuit 124 receives the first, second, and third constantvoltage V1-V3 output from the constant voltage generating circuit 122,and exclusively selects one of the first, second, and third constantvoltage V1-V3 in response to the control signal output from the chargecontrol circuit 108. The selected voltage is output to the controlcircuit 26.

Several components shown in FIG. 4 can be integrated into a single IC(integrated circuit) chip, including the adapter circuit 2, the voltagedetecting circuit 3, the current detecting circuit 6, the charge-enddetecting circuit 7, the charge control circuit 108, and severalcomponents of the CCCV charging circuit 4 including the constant currentreference signal generating circuit 21, the constant voltage generatingcircuit 22, the signal switching circuit 23, the voltage switchingcircuit 24, and the control circuit 26. In addition, the diode 27 canalso be integrated into the above-mentioned single IC chip.

Referring to FIG. 5, an exemplary operation of the charging apparatus100 is explained. In FIG. 5, three time charts are combined togetherusing a common time span. The combined three charts are similar to thoseof FIG. 2, except for A3 a which represents a characteristic curve of avoltage Va 3 output from the voltage switching circuit 124.

The charge control circuit 108 receives, from the adapter detectingcircuit 2, a signal indicating an event that the AC adapter 10 appliespower to the charging apparatus 1 by being connected to the power sourceterminal 15. Then, the charge control circuit 108 starts the chargecontrol at the time point Ts. The charge control circuit 108 controlsthe signal switching circuit 23 to output the first predetermined CCRsignal S1 and also the voltage switching circuit 124 to output the firstpredetermined constant voltage V1. Based on these actions, the controlcircuit 26 controls the operations of the control transistor 25 suchthat the battery voltage Vb indicated by the signal from the voltagedetecting circuit 3 is substantially equal to the first predeterminedconstant voltage V1 and such that the signal from the current detectingcircuit 6 indicates that the charging current ib is substantially equalto the first predetermined constant current i1, so that pre-charging isperformed relative to the lithium ion battery 11 during the time periodT1.

When the battery voltage Vb reaches the first set voltage Vs1, thecharge control circuit 108 controls the signal switching circuit 23 tooutput the second predetermined CCR signal S2 and the voltage switchingcircuit 124 to output the second predetermined constant voltage V2.Accordingly, the control circuit 26 controls the operations of thecontrol transistor 25 such that the battery voltage Vb indicated by thesignal from the voltage detecting circuit 3 is substantially equal tothe second predetermined constant voltage V2 and such that the signalfrom the current detecting circuit 6 indicates that the current ib issubstantially equal to the second predetermined constant current i2. Asa result, the quick charge is performed relative to the lithium ionbattery 11. The operations of the pulse charge, the CC charge, and theCV charge performed after the quick charge are similar to thoseexplained above with reference to FIG. 2 and therefore the explanationsare omitted.

Referring to FIGS. 6, 6A, and 6B an exemplary procedure of the operationperformed by the charge control circuit 108 is explained. The procedureof FIGS. 6, 6A, and 6B is similar to that shown in FIGS. 3, 3A, and 3B,except for Steps S21 and S22 which replace Steps S2 and S4,respectively, shown in FIG. 3A.

In FIGS. 6, 6A, and 6B the charge control circuit 108 first performs theprocess of Step S which is described above with reference to FIG. 3A.Steps S1 to S7 are shown in FIG. 6A and Steps S8 to S13 are shown inFIG. 6B. When the charge control circuit 108 determines in Step S1 thatit receives the power-on signal from the adapter detecting circuit 2,the charge control circuit 108 controls the signal switching circuit 23to output the first constant current reference signal S1 and also thevoltage switching circuit 124 to output the first constant voltage V1 soas to perform the pre-charge operation relative to the lithium ionbattery 11, in Step S21. Then, the charge control circuit 108 performsthe process of Step S3. When the charge control circuit 108 determinesin Step S3 that the battery voltage Vb exceeds the first set voltageVs1, the charge control circuit 108 controls the signal switchingcircuit 23 to output the second constant current reference signal S2 andalso the voltage switching circuit 124 to output the second constantvoltage V2 so as to perform the quick charge operation relative to thelithium ion battery 11, in Step S22. After that, the charge controlcircuit 108 performs the processes of Steps S5-S13 and then terminatesthe process.

In this way, the nonaqueous second charging apparatus 100 of FIG. 4performs the charging operation similar to that of the chargingapparatus 1 of FIG. 1, except for the above-described process in whichthe charging apparatus 100 causes the voltage switching circuit 124 tooutput the first constant voltage V1 during the time period T1 for thepre-charge process and the second constant voltage V2 during the timeperiod T2 for the quick charge process. Therefore, in addition to thecharging performance similar to that of the charging apparatus 1, thecharging apparatus 100 has the following features. That is, the controlcircuit 26 accurately controls the battery voltage Vb to be no greaterthan the first constant voltage V1 in the pre-charge process (duringtime period T1) and also to be no greater than the second constantvoltage V2 in the quick charge process (during time period T2).Therefore, it becomes possible to prevent a problem in that the pulsecharge process erroneously starts before the pre-charge or the quickcharge process is entirely completed if for any reason the batteryvoltage Vb is raised. For example, the above problem may occur when anonaqueous second battery is discharged to an extent of an overdischarge state, resulting in a deterioration of the battery. Also, thisproblem may cause a considerable loss of electric power to the controltransistor, resulting in a production of a great amount of heat.However, the charging apparatus 100 having the above-described featurescan prevent these problems.

1. A battery charging apparatus which charges a battery, comprising: avoltage detecting circuit arranged and configured to detect a batteryvoltage of said battery and for outputting a signal in response to adetected battery voltage; a current detecting circuit arranged andconfigured to detect a charging current supplied to said battery and foroutputting a signal in response to a detected charging current; acharging circuit arranged and configured to control said chargingcurrent such that said detected battery voltage increases to becomesubstantially equal to a first pre-set voltage in response to a firstinput control signal and also such that [[a]] said detected chargingcurrent becomes substantially equal to a constant current predeterminedin response to a second input control signal; and a charge controlcircuit that instructs said charging circuit by said first and saidsecond input control signals to set said first pre-set voltage and saidconstant current in response to said signal from said voltage detectingcircuit.
 2. The battery charging apparatus as defined in claim 1,wherein the charge control circuit is arranged and configured toinstruct the charging circuit to perform [[a]] constant current chargingto flow a first constant current to the battery and subsequently to flowa second constant current greater than the first constant current to thebattery when the detected battery voltage of the battery is smaller thana second pre-set voltage, and to instruct the charging circuit toperform pulse charging, in which flowing current to said battery andpausing current flow to said battery are alternately performed atintervals of a pre-determined time period.
 3. The battery chargingapparatus as defined in claim 2, wherein the charge control circuitinstructs the charging circuit to control the charging current flowingto the battery such that a charging voltage applied across said batterybecomes substantially equal to a third constant voltage during theconstant current charging during the pulse charging and also such thatthe charging voltage becomes substantially equal to a first constantvoltage smaller than the third constant voltage during the pausing inthe pulse charging.
 4. The battery charging apparatus as defined inclaim 3, wherein the charge control circuit instructs the chargingcircuit to perform the constant current charging to supply the secondconstant current to the second battery when the battery voltage becomessubstantially equal to a third pre-set voltage greater than the secondpre-set voltage and also to perform constant voltage charging to controlthe charging current such that the charging voltage becomessubstantially equal to the third constant voltage when the batteryvoltage becomes substantially equal to a fourth pre-set voltage greaterthan the third pre-set voltage.
 5. The battery charging apparatus asdefined in claim 3, wherein the charge control circuit instructs thecharging circuit to control the charging current flowing through thebattery such that the charging voltage becomes substantially equal tothe third constant voltage during the constant current charging beforethe pulse charging is executed. 6-8. (canceled)
 9. The battery chargingapparatus as defined in claim 2, further comprising a charge-enddetecting circuit that determines an event that indicates a charging iscompleted relative to the battery and outputs a predetermined signalwhen the charging current detected by the current detecting circuitbecomes lower than the first constant current, and wherein the chargecontrol circuit causes the charging circuit to stop the charging uponreceiving the signal indicative of a charge end output from thecharge-end detecting circuit.
 10. The battery charging apparatus asdefined in claim 3, wherein the first constant voltage is a voltagegreater than an over discharge voltage of the battery and the thirdconstant voltage is a voltage substantially equal to a full chargevoltage of the battery. 11-12. (canceled)
 13. The battery chargingapparatus as defined in claim 1, wherein the battery is a nonaqueousbattery.
 14. The battery charging apparatus as defined in claim 1,wherein the battery is a lithium ion battery.
 15. A charging method fora battery, comprising the steps of: first performing a first constantcurrent charging by supplying a first constant current to the batterywhen a battery voltage of the battery is smaller than a first pre-setvoltage; second performing a second constant current charging bysupplying a second constant current greater than the first constantcurrent to the battery when the battery voltage of the battery isgreater than the first pre-set voltage; and operating a pulse chargingof the battery when the battery voltage of the battery increases to beequal to or greater than a second pre-set voltage greater than the firstpre-set voltage by alternately carrying out, at intervals of apredetermined time period, a constant current charging in which thesecond constant current is supplied to the battery and a pausing inwhich the supply of the constant current charging is stopped.
 16. Thecharging method as defined in claim 15, wherein the operating stepcomprises controlling a charging current to the battery such that acharging voltage of the battery becomes substantially equal to a thirdconstant voltage during the constant current charging of the pulsecharging and such that the charging voltage of the battery becomessubstantially equal to a first constant voltage smaller than the thirdconstant voltage during the pausing of the pulse charging.
 17. Thecharging method as defined in claim 16, further comprising steps offirst executing a constant current charging in which the constantcurrent charging with the second constant current is performed to thebattery when the battery voltage of the battery becomes substantiallyequal to the third pre-set voltage greater than the second pre-setvoltage and second executing a constant voltage charging in which thecharging current is controlled such that the charging voltage of thebattery becomes substantially equal to the third constant voltage whenthe battery voltage of the battery becomes substantially equal to afourth pre-set voltage greater than the third pre-set voltage.
 18. Thecharging method as defined in claim 16, wherein the charging current tothe battery is controlled such that the charging voltage of the batterybecomes substantially equal to the third constant voltage during thefirst and second constant current charging.
 19. (canceled)
 20. Thecharging method as defined in claim 15, further comprising steps ofdetermining that the charging is completed when the charging current tothe battery becomes substantially equal to a predetermined current valuesmaller than the first constant current and subsequently terminating thecharging to the battery.
 21. The charging method as defined in claim 15,wherein the battery is a nonaqueous battery.
 22. The charging method asdefined in claim 15, wherein the battery is a lithium ion battery.
 23. Abattery charging apparatus which charges a battery, comprising: avoltage detecting circuit arranged and configured to detect a batteryvoltage of said battery and for outputting a signal in response to adetected battery voltage; a current detecting circuit arranged andconfigured to detect a charging current supplied to said battery and foroutputting a signal in response to a detected charging current; acharging circuit arranged and configured to control said chargingcurrent such that said detected battery voltage increases to becomesubstantially equal to a first pre-set voltage in response to an inputcontrol signal and also such that said detected charging current becomessubstantially equal to a constant current predetermined in response tothe input control signal; and a charge control circuit that instructssaid charging circuit by the input control signal to set said firstpre-set voltage and said constant current in response to said signalfrom said voltage detecting circuit.
 24. The battery charging apparatusas defined in claim 23, wherein the charge control circuit is arrangedand configured to instruct the charging circuit to perform constantcurrent charging to flow a first constant current to the battery andsubsequently to flow a second constant current greater than the firstconstant current to the battery when the detected battery voltage of thebattery is smaller than a second pre-set voltage, and to instruct thecharging circuit to perform pulse charging, in which flowing current tosaid battery and pausing current flow to said battery are alternatelyperformed at intervals of a pre-determined time period.
 25. The batterycharging apparatus as defined in claim 24, wherein the charge controlcircuit instructs the charging circuit to control the charging currentflowing to the battery such that a charging voltage applied across saidbattery becomes substantially equal to a third constant voltage duringthe constant current charging during the pulse charging and also suchthat the charging voltage becomes substantially equal to a firstconstant voltage smaller than the third constant voltage during thepausing in the pulse charging.
 26. The battery charging apparatus asdefined in claim 25, wherein the charge control circuit instructs thecharging circuit to perform the constant current charging to supply thesecond constant current to the battery when the battery voltage becomessubstantially equal to a third pre-set voltage greater than the secondpre-set voltage and also to perform constant voltage charging to controlthe charging current such that the charging voltage becomessubstantially equal to the third constant voltage when the batteryvoltage becomes substantially equal to a fourth pre-set voltage greaterthan the third pre-set voltage.
 27. The battery charging apparatus asdefined in claim 25, wherein the charge control circuit instructs thecharging circuit to control the charging current flowing through thebattery such that the charging voltage becomes substantially equal tothe third constant voltage during the constant current charging beforethe pulse charging is executed. 28-31. (canceled)
 32. The batterycharging apparatus as defined in claim 25, wherein the first constantvoltage is a voltage greater than an over discharge voltage of thebattery and the third constant voltage is a voltage substantially equalto a full charge voltage of the battery.
 33. The battery chargingapparatus as defined in claim 28, wherein the current detecting circuitcomprises: a resistor through which the charging current to be suppliedto the battery flows; and a current detector that detects the chargingcurrent based on a voltage across the resistor and outputs a signal inresponse to the detected charging current, wherein the voltage detectingcircuit, the current detector of the current detecting circuit, thecharge control circuit, a charge-end detecting circuit, and severalcomponents of the charging circuit including a constant voltagegenerating circuit, a voltage switching circuit, a constant currentreference signal generating circuit, a signal switching circuit, and acontrol circuit are integrated into a single integrated circuit chip.34. The battery charging apparatus as defined in claim 30, wherein thecurrent detecting circuit comprises: a resistor through which thecharging current to be supplied to the battery flows; and a currentdetector that detects the charging current based on a voltage across theresistor and outputs a signal in response to the detected chargingcurrent, wherein the voltage detecting circuit, the current detector ofthe current detecting circuit, the charge control circuit, a charge-enddetecting circuit, and several components of the charging circuitincluding a constant voltage generating circuit, a voltage switchingcircuit, a constant current reference signal generating circuit, asignal switching circuit, and a control circuit are integrated into asingle integrated circuit chip.
 35. The battery charging apparatus asdefined in claim 23, wherein the battery is a nonaqueous battery. 36.The battery charging apparatus as defined in claim 23, wherein thebattery is a lithium ion battery.